Alan: Cardio 2x per day

[t-bone2]

Alan,

I've seen (and respect) the various articles you've written regarding cardio. I came across an article (excerpt below) that I hope you'll comment on. If, in order to oxidize FFAs, they need to first be mobilized and transported, I'm having difficulty seeing how two 15 minute cardio sessions per day will burn more calories that a single 30 minute session, unless the 2 session are at a significantly higher heart rate for the duration than the single session.

Any insight would be helpful.

"Just by cutting your usual 30 minute cardio session into two 15 minute sessions per day can nearly double your benefits but utilizing almost double the amount of calories. Researchers at the University of Kansas investigated this topic and published the results in the Canadian Journal of Physiology (23:433-443, 1998). These scientists took 18 male subjects and asked them to perform two different training sessions on different occasions, but both exercise sessions were of equal intensity. On the first occasion the men exercised for a straight 30 minutes. On the another occasion they exercised for two 15-minute sessions separated by six hours. Post-exercise oxygen consumption (EPOC) was used to assess the amount of calories burnt from the exercise.

"Results showed that although the total training time and intensity level were equal, when the men exercised twice in one day they burnt almost twice as many calories compared to the one off bout. That is a very big difference.

"However, training twice a day doesn't necessarily mean double the work load. Two bursts of around 15 minutes of high intensity work may be much more effective than one long session for achieving the results you want.

 

[Kam]

My only guess is the post effects of the workouts are different, u have one long session you body metabolism is flying for 4-5 hours, but you go twice your getting 3-4 hours after each workout meaning your burning more calories because of the seperation of exercises. Like keeping a buzz in a way, you can go nuts for 30 minutes it last 2 hours or you indulge for 15 minutes it lasts an hour and a half and then you do it again and it last another hour and a half. lol hope some of this makes sense.

I like to do a morning cardio and then a short pre and post cardio during the weight training set later in the day, maybe 4-5 hours after morning cardio

 

[Pfunk47]

to me it makes sense to look it as a wave diagram - with the first 15 mins you ascend your heart rate and FFA oxidation then you start to descend as the day goes on but you ascend again with another 15 mins - keeping your levels/heart rate at a much higher average opposed to 30 mins where you ascend descend at about the same rate as 15 mins but you just stayed at a much higher peak within that 30 mins - your daily average would be lower. just my thoughts.

 

[t-bone2]

I don't think you're going to be doing much oxidization in the first 15 minutes - I think that would primarily be where FFAs would begin to get mobilized and subsequently transported, especially in areas where blood flow is significantly impaired. I think that the oxidization would mostly occur toward the tail end and then residually flow into the time after completion of the session. But for how long will FFAs continue to be oxidized?

Also, will an intense 15 minute session increase catecholamines to a level which will inhibit oxidization in the muscles - or is this the "sweet spot?"

 

[alan aragon]

Alan,

I've seen (and respect) the various articles you've written regarding cardio. I came across an article (excerpt below) that I hope you'll comment on. If, in order to oxidize FFAs, they need to first be mobilized and transported, I'm having difficulty seeing how two 15 minute cardio sessions per day will burn more calories that a single 30 minute session, unless the 2 session are at a significantly higher heart rate for the duration than the single session.

Any insight would be helpful.

"Just by cutting your usual 30 minute cardio session into two 15 minute sessions per day can nearly double your benefits but utilizing almost double the amount of calories. Researchers at the University of Kansas investigated this topic and published the results in the Canadian Journal of Physiology (23:433-443, 1998). These scientists took 18 male subjects and asked them to perform two different training sessions on different occasions, but both exercise sessions were of equal intensity. On the first occasion the men exercised for a straight 30 minutes. On the another occasion they exercised for two 15-minute sessions separated by six hours. Post-exercise oxygen consumption (EPOC) was used to assess the amount of calories burnt from the exercise.

"Results showed that although the total training time and intensity level were equal, when the men exercised twice in one day they burnt almost twice as many calories compared to the one off bout. That is a very big difference.

"However, training twice a day doesn't necessarily mean double the work load. Two bursts of around 15 minutes of high intensity work may be much more effective than one long session for achieving the results you want.

To quote world EPOC authorities Borsheim & Bahr in a comprehensive review of research [Sports Med 2003; 33(14):1037-60], including the 1998 study you cited,

"It should be noted that even though EPOC is higher after split sessions, the extra EPOC is small in relation to the exercise energy expenditure. Thus, prolonging the exercise bout by a few minutes may make up for the increase in EPOC after splitting the session."

Basically, although the caloric expenditure is more as a result of splitting the session into 2 shorter ones, the actual amount of extra calories burned is too insignificant to write home about.

 

[t-bone2]

Ok, that's along the lines of were I thought it was going to end up. Otherwise I could split up my single 45 minute session into three seperate 15 minute sessions and perform some serious oxidation - BAM!

Thanks for your insight and the journal reference.

 

[drumirvin]

I have been using HIIT for over two years pre-contest and found it to work more than any other type of cardio. 15min on the bike both times with 30 sec on/30 off is my preference. I try to stay on the bike to minimize any muscle breakdown in my legs. I find that the stepper kills my quad sweep and the elliptical just pisses me off. I do walk for 30 minutes sometimes at a 3.4 setting and up to 4.5 incline to break up the monotony of having to do cardio. I hate cardio.

 

[rippedforce63]

Funny how everyones different, I saw an improvement in my legs when I started doing the stepper.

 

[UNCCFitness]

not to sound like a smarty but we've been studyin this topic in exercise physiology (im a senior in college, exercise science major)

Splitting the cardio into two sessions (ESPECIALLY 15 minutes long) is NOT a good idea for fat loss. Beta oxidation doesn't kick in until 10-15 minutes because until then you rely on ATP-CP/glycolysis, neither of which can break fat down alone. Fat MUST go through beta-oxidation before it can be broken in the krebs cycle/ETC for energy.

EVERY article i've seen out of the journal for applied physiology has agreed, the longer your bout of cardio is, the more fat you burn. Longer bouts of cardio, at around 50-60% VO2max have been clinically repeated time and time again to be THE best range to burn fats, and as time increased the % of cals from fats increased too. They measure that by strapping people to machines measuring their respiratory output. You can measure how much fat you burn vs. how much carb you burn by measuring the ammounts of O2 and CO2 in your exhaled breath.

HIIT might cause a greater calorie deficit, however going from high to low intensity will be taxing the atp-cp/glycolysis/krebs cycle... NOT beta oxidation. and until you get them fats moving thru beta oxidation, you cant do **** with them. the greater calorie deficit will come out of the sugar stores all over ur body (glycogen etc...) not fat.

 

[drumirvin]

UNCC, I totally agree on some aspects of what the "books" say...trial and error my friend. You go with what works for you..Here is one study concerning HIIT..

HIIT
(20 week program, 17 subjects)


Mode (ergocycle) Endurance Training High Intensity Interval Training
Duration (minutes) 30 and increased to 45 30
Frequency 4/wk and increased to 5/wk 25 continuous sessions; half completed before week 5

Week 5-20: 19 long & 16 short interval sessions

Intensity 60% HRR and increased to 85% HRR 70% HRR warmup

60% of max output in 10 seconds & 70% of max output in 90 seconds; increasing 5% every 3 weeks

Energy Expended (MJ) 120.4 ± 31.0 57.9 ± 14.4
Fat Loss (mm) 4.5 13.9


High Intensity Interval Training (HIIT)
5 minute warm-up at 50% HRR
Short-interval work
Initially 10 and later 15 bouts
15 seconds increasing to 30 seconds
Long-interval
4 to 5 bouts
60 seconds increasing to 90 seconds
Bouts separated by recovery periods allowing heart rate to return to 120 to 130 bpm
Creatine phosphate recovery may take 4 minutes to replete beteem maximal bouts
Fat Loss measured in millimeters
Difference of before and after sum of skin fold measurements
Sum of skin folds
Triceps, Biceps, Calf, Subscapular, Suprailiac, Abdomen
Also see SIT Guidelines and Sample Programs.

The HIIT group lost over 3 times as much subcutanious fat as the ET group despite of only expending less than half as many calories.

--------------------------------------------------------------------------------


Trembblay A, Simoneau JA, Bouchard C. (1994). Impact of Exercise Intensity on Body Fatness and Skeletal Muscle Metablism, Metabolism. 43(7): 814-818.

 

[UNCCFitness]

what journal does that study come from?

anything published that's not peer-reviewed is garbage. I can write an article and post it somewhere, but there are only 2-3 professional journals that are peer-reviewed by the top experts in the world.

 

[Dwight Schrute]

what journal does that study come from?

anything published that's not peer-reviewed is garbage. I can write an article and post it somewhere, but there are only 2-3 professional journals that are peer-reviewed by the top experts in the world.

I wouldn't say that at all. There are plenty of studies that have been conducted and not published in peer reviewed journals because of other circumstances.

When you compare HIIT to low intensity you should really compare it to Low intesnity cardio + a resistance training program because the hormonal response is similar when its combined. HIIT more resembles a weight training session (when it comes to hormonal and physiological differences) than low intensity therefore the comparison really isn't valid when compared straight up.

 

[drumirvin]

UNCC, you are correct when concerned for peer reviewed articles about HIIT cardio. Not much to go on other than private studies and individual testimony. Bobo nailed it when referring to hormonal response. The burst of intensity required in a short amount of time coupled with your daily routine causes the motion for fat burning..I am not preaching that HIIT is the Gosple of cardio nor is it the final word and that everyone should be doing it. What I do believe is, for bodybuilders, it works. The lower intensity "leaves" muscle alone and creates just the right intensity for the metabolism to stay elevated through out the day until the next bout of 15minutes. Just enough fat burning without the cannibalizing of the muscle. I may be wrong in my assumption but through my processes I find that HIIT is what really helps me...(MIKE) when coming to losing weight. I do like to go for a LONG run everynow and then as well as a long bike ride..I guess I am just trying to find an excuse for not "cardioing" any more than I have to. Dern that damn cardio....

 

[UNCCFitness]

i semi-agree with you bobo... because thats what i do. I usually lift for about 45 minutes, which taxes alot of the sugars floatin around. Then do 30-60 mins of steady state cardio at around 55-60% VO2max... it works wonders for me, i respond to it better than HIIT

i definately feel that everyone HAS to try a variety of things and see what works for THEM.

and i understand what ur sayin bout the two bouts having a greater impact on overall metabolism... but to me, 15 minutes isnt long enough to be in beta-oxidation... without beta-oxidation you dont burn fat. If you do cardio for 15 mins. (just cardio... not after lifting) then eat something, you wont burn any fat. all those cals will be converted to sugars to replace your stores... so you really netted no loss in fat... but overall you might have "burned" more calories. thats just my understanding and personal experience.

because no matter how many people you study... everyone is still different :gas:

 

[loki82]

UNNCCFitness, if i could ask you, you said that fat oxidation doesn't start around 10-15 cardio then after that fat oxidation begins to work. Well I just started get my life back together and i'm morbidly obese and really really out of shape. So on cardio, i split up 3 10 minute sessions switching back and forth to the ellipitcal and treadmill, I keep my heart rate up at 160. on your statement, does this mean that splitting my cardio to 3 10 minute sessions isn't very good? if it isn't i'll just go 30 minutes strait, but i'm not every confident i can keep up the pace at 160 bpm. but i guess in due time that'll change.

 

[alan aragon]

what journal does that study come from?

anything published that's not peer-reviewed is garbage. I can write an article and post it somewhere, but there are only 2-3 professional journals that are peer-reviewed by the top experts in the world.

That Tremblay study is one of the most famous HIIT studies to date. Get to studying, private Pile

Also, you seem stuck on substrate use DURING training, versus the other 90% of your time in the day. Gotta look at the whole picture, not a small fraction. By the day's end, low intensity stuff is NOT inherently more fat-burning than higher intensity stuff. This has been measured & published several times. I've taught classes for ex-phys majors, and it's amazing how few of them understand & are aware of this research.

If you're pressed for time, and you can do HIIT without any DOMS overlap (by virtue of doing a low frequency of it), and you can tolerate it joint-wise & heart-wise, and you hate spending time doing cardio to begin with, then booyah -- do HIIT. On the other hand, if you have the time to allot for LISS, and you do a lot of resistance training which raises recovery conflicts posed by a lot of HIIT, then kapowee -- do LISS. If you're somewhere in between the aforementioned 2 camps and you don't have a specific preference or tolerance limit, do both types on either a cyclical, rotational, or even combined basis.

Bobo is right in that HIIT has a similar metabolic effect to weight training, so it may be a redundant or recovery-challenging practice when your weight training volume or frequency is already high. I can appreciate his position on this. I on the other hand have a personal preference for HIIT because I have a deep seated hate for doing cardio in the 1st place. So when I do it at all, I keep my cardio time minimal by infusing as much intensity as possible, positioning the bout away from DOMS interference, & keeping the frequency as low as possible.

This is just my personal situation, and remember that the more bodymass you have, the riskier it becomes to chronically do a lot of HIIT as an exclusive mode of cardio. This is one of the reasons pros avoid it. They have the time in the day to do LISS, and it benefits them to cut their injury risk as much as possible. It can't be overstated that unless you undergo a very gradual progression towards the the musculoskeletal tolerance for something like sprinting, your ass can get hurt pretty bad & there goes your productive training for several weeks. Conversely, I know guys who can do a ton of HIIT on top of their bodybuilding programs, even in precontest mode. This is a function of having progressed to this point, and having done it this way for quite a long time. Others will undoubtedly have different preferences & tolerances for various cardio types.

I see the bottom line like this.. Do the type you have a personal preference for, and also respect your physical limits. HIIT is quicker but riskier. LISS is safer but takes twice as long to accomplish the same thing. Again, do what you prefer & can tolerate, but do NOT make the mistake of assuming that LISS burns more fat. That's misunderstanding the physiology of the matter.

 

[t-bone2]

HIIT is quicker... LISS...takes twice as long to accomplish the same thing.

Alan,

All else being equal, is the 2:1 (HIIT:LISS) ratio a broad generalization here? Or should the statement be that HIIT is more efficient, but there are too many variables to say how much more efficient?

Also, could you elaborate further on DOMS relative to when HIIT is performed? Is this basically, do it if you can personally handle it or is there a physiological reason to not do HIIT until recovered from DOMS?

 

[alan aragon]

Alan,

All else being equal, is the 2:1 (HIIT:LISS) ratio a broad generalization here? Or should the statement be that HIIT is more efficient, but there are too many variables to say how much more efficient?

Also, could you elaborate further on DOMS relative to when HIIT is performed? Is this basically, do it if you can personally handle it or is there a physiological reason to not do HIIT until recovered from DOMS?

1) This is a generalization, but it's within the ballpark of reality. True that there are many possible variations that could confound the "absoluteness" of the statement (ie, length of intervals, actual intensity, etc).

2) Training sore muscles - with enough frequency - would slow down your rate of recovery. Physiologists make a distinction between muscle fatigue (reversible within minutes or hours) & muscle damage (reversible within days). Muscle fatigue is basically the accumulation or depletion of various cellular metabolites and ions. Muscle damage, which is for the most part ECCENTRICALLY induced, is characterized by sarcomeric disturbances & irregularitues. To a certain degree, muscle damage is obviously necessary for the hypertrophic response. But, the potential danger of adding "insult to injury" pushes muscle damage to counterproductive levels that stall progress.

Muscle damage forces myofibrillar ionic changes, including but not limited to elevated calcium & sodium retention (instead of release like it should), and decreased pH, all via membrane tears, leak channels & a number of other ion flux means. Consequently, these ionic changes can reduce force production via creating regions of over & understretched sarcomeres, which in simple terms, screw up the muscle's length-tension relationship (particularly towards length instead of tension). What happens is a decline of force at the original optimum length. Another mechanism among many possibilities is the impairment of excitation–contraction coupling.

Training DOMS-ridden muscles will only accelerate the above mentioned processes, which logically would accelerate muscle damage, and thus put your cyclic microtrauma:recovery ratio in the positive, which ultimately would either stall your gains, or force your body into an injury-induced layoff. Training with DOMS is an interesting area of study. Ironically, there is some research floating around out there (read it a while back) regarding strength protocols that occassionally implement successive exhaustive training days of the same muscle group. I guess you can think of it as periodized overtraining, keyword is occasionally. DOMS training overlap will also depend on a lot of factors, not the least of which is degree of DOMS in the 1st place. Theory is one thing, but application is another animal completely, since everyone's protocol & tolerance is gonna vary. I would still not recommend training sore muscles in any case. I'm sure someone can compile all the known research & build a case for occasional or periodic overtraining (including training sore muscles), but on a gut/instictive level, I personally would not do it to myself.

 

[alan aragon]

Wow I'm a pretty long-winded bastard

 

[t-bone2]

Wow I'm a pretty long-winded bastard

Yeah, a veritable walking encyclopedia I appreciate the detailed response - it's helpful to know the science behind the "do it this way."